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12 Oct 1998

Volume 73, Issue 15, pp. 2069-2222

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Interlayer exchange in (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As semiconducting ferromagnet/nonmagnet/ferromagnet trilayer structures

N. Akiba, F. Matsukura, A. Shen, Y. Ohno, H. Ohno, A. Oiwa, S. Katsumoto, and Y. Iye

Appl. Phys. Lett. 73, 2122 (1998); http://dx.doi.org/10.1063/1.122398 (3 pages) | Cited 26 times

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Magnetic properties of all-semiconductor (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As trilayer structures are studied. The interactions between the two ferromagnetic (Ga,Mn)As layers are investigated by magnetotransport measurements in a number of samples with different GaAs thickness or with different Al content in the intermediary nonmagnetic (Al,Ga)As layer. The results indicate that carriers present in the nonmagnetic layer mediate the coupling between the two ferromagnetic layers. © 1998 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.50.Pp Magnetic semiconductors
75.30.Et Exchange and superexchange interactions
71.70.Gm Exchange interactions
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

High-quality germanium photodiodes integrated on silicon substrates using optimized relaxed graded buffers

S. B. Samavedam, M. T. Currie, T. A. Langdo, and E. A. Fitzgerald

Appl. Phys. Lett. 73, 2125 (1998); http://dx.doi.org/10.1063/1.122399 (3 pages) | Cited 44 times

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The integration of Ge photodetectors on silicon substrates is advantageous for various Si-based optoelectronics applications. We have fabricated integrated Ge photodiodes on a graded optimized relaxed SiGe buffer on Si. The dark current in the Ge mesa diodes, Js = 0.15 mA/cm2, is close to the theoretical reverse saturation current and is a record low for Ge diodes integrated on Si substrates. Capacitance measurements indicate that the detectors are capable of operating at high frequencies (2.35 GHz). The photodiodes exhibit an external quantum efficiency of η = 12.6% at λ = 1.3 μm laser excitation in the photodiodes. The improvement in Ge materials quality and photodiode performance is derived from an optimized relaxed buffer process that includes a chemical mechanical polishing step within the dislocated epitaxial structure. © 1998 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
42.82.Bq Design and performance testing of integrated-optical systems
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
42.86.+b Optical workshop techniques
81.65.Ps Polishing, grinding, surface finishing
72.40.+w Photoconduction and photovoltaic effects

Giant acoustoelectric effect in GaAs/LiNbO3 hybrids

M. Rotter, A. Wixforth, W. Ruile, D. Bernklau, and H. Riechert

Appl. Phys. Lett. 73, 2128 (1998); http://dx.doi.org/10.1063/1.122400 (3 pages) | Cited 13 times

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The acoustoelectric effect in a hybrid of a strong piezoelectric material and a semiconductor layer containing a two-dimensional electron system is investigated. Caused by the very strong interaction between a surface acoustic wave and the mobile carriers in the semiconductor, the acoustoelectric effect is very large as compared to other materials, which might be interesting for device applications. Moreover, the tunability of the sheet conductivity of the electron system enables us to tune the magnitude of the acoustoelectric effect over a wide range. We present experimental results for a GaAs/LiNbO3 layered hybrid system at room temperature and describe our experimental findings quantitatively using a recently developed model calculation. © 1998 American Institute of Physics.
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73.50.Rb Acoustoelectric and magnetoacoustic effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
68.35.Gy Mechanical properties; surface strains
43.35.Pt Surface waves in solids and liquids

Neutron reflectometry, x-ray reflectometry, and spectroscopic ellipsometry characterization of thin SiO2 on Si

J. A. Dura, C. A. Richter, C. F. Majkrzak, and N. V. Nguyen

Appl. Phys. Lett. 73, 2131 (1998); http://dx.doi.org/10.1063/1.122442 (3 pages) | Cited 12 times

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We present here a comparison of neutron reflectometry, x-ray reflectometry, and spectroscopic ellipsometry on a thin oxide film. These three probes each independently determine the structure of the film as a function of depth. We find an excellent agreement between the three techniques for measurements of thicknesses and interfacial roughnesses for both the SiO2 and surface contamination layers found in the sample. Realistic models based on interface parameters measured herein indicate that as the SiO2 layers decrease to sizes projected for future generations of electronic devices, both spectroscopic ellipsometry and neutron reflectometry can easily measure SiO2 films to 2 nm thick or less.
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68.55.-a Thin film structure and morphology
68.35.Ct Interface structure and roughness
77.55.-g Dielectric thin films

Silicon single electron memory cell

N. J. Stone and H. Ahmed

Appl. Phys. Lett. 73, 2134 (1998); http://dx.doi.org/10.1063/1.122401 (3 pages) | Cited 32 times

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A compact single-electron memory cell has been fabricated in silicon using a process that is compatible with complementary metal–oxide–semiconductor circuit fabrication. The device is based on the Coulomb blockade effect observed in highly doped silicon nanowires. The circuit shows clear memory operation with a >100 mV gap between “0” and “1” levels when tested at a temperature of 4.2 K. The response of the circuit to write and erase pulse sequences is also presented. © 1998 American Institute of Physics.
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85.35.Gv Single electron devices
73.23.Hk Coulomb blockade; single-electron tunneling

Layered tunnel barriers for nonvolatile memory devices

Konstantin K. Likharev

Appl. Phys. Lett. 73, 2137 (1998); http://dx.doi.org/10.1063/1.122402 (3 pages) | Cited 90 times

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Fowler–Nordheim tunneling of electrons through “crested” energy barriers (with the height peak in the middle) is much more sensitive to applied voltage than that through barriers of uniform height. Calculations for trilayer barriers, with layer parameters typical for wide-band-gap semiconductors, have shown that by merely doubling the voltage, the tunnel current may be changed by more than 16 orders of magnitude. It is argued that this effect may be used for the implementation of nonvolatile random-access memories combining a few ns cycle time with a few years retention time and for ultradense electrostatic data storage. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
85.35.Gv Single electron devices
73.40.Gk Tunneling

Room temperature spin relaxation in GaAs/AlGaAs multiple quantum wells

R. S. Britton, T. Grevatt, A. Malinowski, R. T. Harley, P. Perozzo, A. R. Cameron, and A. Miller

Appl. Phys. Lett. 73, 2140 (1998); http://dx.doi.org/10.1063/1.122403 (3 pages) | Cited 39 times

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We have explored the dependence of electron spin relaxation in undoped GaAs/AlGaAs quantum wells on well width (confinement energy) at 300 K. For wide wells, the relaxation rate tends to the intrinsic bulk value due to the D’yakonov–Perel (DP) mechanism with momentum scattering by phonons. In narrower wells, there is a strong dependence of relaxation rate on well width, as expected for the DP mechanism, but also considerable variation between samples from different sources, which we attribute to differences in sample interface morphology. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
71.35.Ee Electron-hole drops and electron-hole plasma
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Green emission from Er-doped GaN grown by molecular beam epitaxy on Si substrates

R. Birkhahn and A. J. Steckl

Appl. Phys. Lett. 73, 2143 (1998); http://dx.doi.org/10.1063/1.122404 (3 pages) | Cited 30 times

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Visible light emission has been obtained from Er-doped α-GaN thin films grown on Si(111). The GaN was grown by molecular beam epitaxy using solid sources (for Ga and Er) and a plasma gas source for N2. Photoexcitation with a He–Cd laser resulted in strong green emission from two narrow green lines at 537 and 558 nm identified as Er transitions from the 2H11/2 and 4S3/2 levels to the 4I15/2 ground state. X-ray diffraction shows the GaN:Er to be a wurtzitic single crystal film. The growth temperature is seen to have a strong effect on the GaN:Er surface morphology. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)

AlxGa1−xN:Si Schottky barrier photodiodes with fast response and high detectivity

E. Monroy, F. Calle, E. Muñoz, F. Omnès, P. Gibart, and J. A. Muñoz

Appl. Phys. Lett. 73, 2146 (1998); http://dx.doi.org/10.1063/1.122405 (3 pages) | Cited 33 times

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Gold and nickel Schottky barrier photovoltaic detectors have been fabricated on Si-doped AlxGa1−xN layers (0 ⩽ x ⩽ 0.22) grown on sapphire by metalorganic vapor phase epitaxy. Responsivity is independent of the Schottky metal or diode size, and also of the incident power in the range measured (10 mW/m2–2 kW/m2). A higher visible rejection has been observed in the spectral response of Au photodiodes (>103). Time response is resistance-capacitance limited, with time constants as short as 14 ns in Al0.22Ga0.78N diodes. Low frequency noise studies are also presented, and detectivities of 6.1×107 and 1.2×107 mHz1/2 W−1 are determined in GaN/Au and Al0.22Ga0.78N/Au detectors, at −2 V bias. © 1998 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
73.50.Pz Photoconduction and photovoltaic effects

Coherent acoustic phonons in PbTe quantum dots

E. R. Thoen, G. Steinmeyer, P. Langlois, E. P. Ippen, G. E. Tudury, C. H. Brito Cruz, L. C. Barbosa, and C. L. Cesar

Appl. Phys. Lett. 73, 2149 (1998); http://dx.doi.org/10.1063/1.122406 (3 pages) | Cited 23 times

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Femtosecond pump-probe studies at 1.5 μm of PbTe quantum dots in a glass matrix have revealed oscillations due to a spheroidal acoustic mode. The wavelength dependence of the observed frequencies indicates size selectivity. The frequency and damping of the mode as a function of wavelength agree with the predictions of an acoustic continuum model that suggests that the dominant damping mechanism is radiative loss from the dots to the surrounding glass. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Le Other inorganic semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.47.-p Spectroscopy of solid state dynamics
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
71.38.-k Polarons and electron-phonon interactions

Evidence of electron confinement in the single-domain (4×1)-In superstructure on vicinal Si(111)

F. Pedreschi, J. D. O’Mahony, P. Weightman, and J. R. Power

Appl. Phys. Lett. 73, 2152 (1998); http://dx.doi.org/10.1063/1.122407 (3 pages) | Cited 20 times

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Reflectance anisotropy spectroscopy is applied to submonolayer growth of In on the vicinal silicon (111) surface. Deposition in the region of 1 monolayer onto a clean stepped Si(111) surface at elevated temperature produces a single-domain In-induced (4×1) superstructure consisting of quasi-one-dimensional chains aligned parallel to the vicinal surface step edges. A significant optical anisotropy (1.65%), uncharacteristic of semiconductor systems, develops in the region of 1.9 eV which saturates upon completion of the (4×1) superstructure. We relate this feature to an optical transition involving a flat, highly populated filled surface state observed previously. We argue that the intensity and direction of this peak are indicative of electronic confinement within this system perpendicular to the In-induced chain length. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
78.66.Bz Metals and metallic alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Two-dimensional carrier profiling of InP structures using scanning spreading resistance microscopy

P. De Wolf, M. Geva, T. Hantschel, W. Vandervorst, and R. B. Bylsma

Appl. Phys. Lett. 73, 2155 (1998); http://dx.doi.org/10.1063/1.122408 (3 pages) | Cited 36 times

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Scanning spreading resistance microscopy (SSRM) is an analytical technique originally developed for measuring two-dimensional carrier distribution in Si device structures with high spatial resolution. It is in essence an atomic force microscope equipped with a conducting tip that is biased relative to the sample. The spreading resistance value derived from the measured electrical current is a function of the local carrier concentration at the surface region surrounding the probe’s tip. In this letter, we report the successful application of SSRM to the analysis of InP semiconductor device structures. We imaged a multilayer epitest structure, and a cross section of a three-dimensional structure in which we observed lateral Zn-dopant diffusion. Comparison of the SSRM profiles with one-dimensional secondary ion mass spectrometry depth profiles shows good qualitative agreement. SSRM analysis of InP-based device structures was found to be much simpler than that of Si structures: there is no need for surface preparation of the cleaved surface, a lower tip force is required, and metal tips, rather than doped diamond can be used. © 1998 American Institute of Physics.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors
68.35.Fx Diffusion; interface formation

Room-temperature pulsed operation of an electrically injected InGaN/GaN multi-quantum well distributed feedback laser

Daniel Hofstetter, Robert L. Thornton, Linda T. Romano, David P. Bour, Michael Kneissl, and Rose M. Donaldson

Appl. Phys. Lett. 73, 2158 (1998); http://dx.doi.org/10.1063/1.122409 (3 pages) | Cited 14 times

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We demonstrate room-temperature pulsed operation of an electrically injected InGaN/GaN-based distributed feedback laser with an emission wavelength of 403 nm. The threshold current of a 1000-μm-long and 20-μm-wide device was 3.2 A; corresponding to a threshold current density of 16 kA/cm2. The 3rd order grating providing feedback was defined holographically and dry etched into the upper waveguiding layer by chemically assisted ion beam etching. We observed single mode operation of the laser with a side mode suppression ratio of 15 dB over a temperature range of about 30 K. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

On the correlation between the carbon content and the electrical quality of thermally grown oxides on p-type 6H–Silicon carbide

Vickram R. Vathulya, Dong Ning Wang, and Marvin H. White

Appl. Phys. Lett. 73, 2161 (1998); http://dx.doi.org/10.1063/1.122562 (3 pages) | Cited 25 times

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Thermal oxides on p-type silicon carbide exhibit high densities of interface states and fixed charge. Understanding the effect of the oxide composition on the electrical properties is imperative to improve the quality of oxides on p-type silicon carbide. In this work, we use angle resolved x-ray photoelectron spectroscopy to profile the oxide composition. The result is a direct correlation between the carbon content in the oxide and the density of interface states and fixed charge as determined by electrical capacitance–voltage measurements. © 1998 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
79.60.Jv Interfaces; heterostructures; nanostructures

Self-organization of (In,Ga)As/GaAs quantum dots on relaxed (In,Ga)As films

Dong Pan, Jian Xu, Elias Towe, Qin Xu, and J. W. Hsu

Appl. Phys. Lett. 73, 2164 (1998); http://dx.doi.org/10.1063/1.122410 (3 pages) | Cited 8 times

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We report the synthesis of (In,Ga)As/GaAs quantum dots on strain-relaxed (In,Ga)As epitaxial films. It is found that the incorporation of a relaxed prelayer provides a systematic and effective method for controlling the dot distribution and emission wavelength. The robustness of the optical properties of quantum dots to dislocations may provide a method for engineering the band structure of quantum dot devices. We demonstrate, for example, that longer band-to-band emission wavelengths can be obtained by simply decreasing the residual strain in the relaxed films. © 1998 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
68.60.Bs Mechanical and acoustical properties

Injection level dependence of the defect-related carrier lifetime in light-degraded boron-doped Czochralski silicon

Jan Schmidt, Christopher Berge, and Armin G. Aberle

Appl. Phys. Lett. 73, 2167 (1998); http://dx.doi.org/10.1063/1.122411 (3 pages) | Cited 11 times

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The carrier recombination lifetime in light-degraded boron-doped 1 Ω cm Czochralski-grown silicon wafers is measured as a function of the bulk excess carrier concentration Δn. The measurements are performed with the quasi-steady state photoconductance method and cover a large injection level range between 1013 and 1.5×1017 cm−3. We observe a very strong increase of the carrier lifetime in the Δn range between 1014 and 2×1016 cm−3, which is attributed to boron–oxygen (BiOi) defect pairs. The observed strong increase of the defect-related carrier lifetime allows us to determine the previously unknown hole capture cross section σp of the BiOi pair. Our analysis gives a σp value of (0.45–1.2)×10−15 cm2, which is 2–3 orders of magnitude smaller than the corresponding electron capture cross section. © 1998 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
72.40.+w Photoconduction and photovoltaic effects

Transmission electron microscopy and photoluminescence studies of Er implanted low-temperature grown GaAs:Be

R. L. Maltez, Z. Liliental-Weber, J. Washburn, M. Behar, P. B. Klein, P. Specht, and E. R. Weber

Appl. Phys. Lett. 73, 2170 (1998); http://dx.doi.org/10.1063/1.122412 (3 pages) | Cited 2 times

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Characteristic 1.54 μm 4f-4f emission has been observed from Er3+ centers in Er-implanted and annealed, low-temperature grown GaAs:Be samples, while cross-sectional transmission electron microscopy (TEM) studies reveal very little structural damage for elevated temperature implants. No Er emission was observed from any of the as-implanted samples, while the Er emission intensity was significantly more intense after 650 °C anneals than after 750 °C anneals. Significant enhancement of the optically active Er incorporation was achieved when the implantation was carried out at 300 °C. For the two total Er fluences employed (5.5×1013 and 13.6×1013 Er/cm2) the Er emission intensity exhibited a linear dependence upon implantation fluence, while TEM indicated no significant increase in the damage level at the higher fluence 300 °C implant. © 1998 American Institute of Physics.
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68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
61.72.uj III-V and II-VI semiconductors
78.55.Cr III-V semiconductors

Current-induced local oxidation of metal films: Mechanism and quantum-size effects

Thomas Schmidt, Richard Martel, Robert L. Sandstrom, and Phaedon Avouris

Appl. Phys. Lett. 73, 2173 (1998); http://dx.doi.org/10.1063/1.122413 (3 pages) | Cited 28 times

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A novel route is introduced for oxidizing thin metal films with nanometer-scale resolution. By locally subjecting Ti and Nb films to high in-plane current densities, metal-oxide tunneling barriers are formed in a self-limiting fashion. The oxidation is triggered by current-induced atomic rearrangements and local heating. At the final stages of the barrier formation, when only atomic-scale channels remain unoxidized, the oxidation rate decreases drastically while the conductance drops in steps of about 2e2/h. This behavior gives evidence of ballistic transport and a superior stability of such metallic nanowires against current-induced forces compared with the bulk metal. © 1998 American Institute of Physics.
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73.61.At Metal and metallic alloys
81.65.Mq Oxidation
73.50.Fq High-field and nonlinear effects
73.50.Mx High-frequency effects; plasma effects

Exciton transport into a single GaAs quantum wire studied by picosecond near-field optical spectroscopy

A. Richter, M. Süptitz, D. Heinrich, Ch. Lienau, T. Elsaesser, M. Ramsteiner, R. Nötzel, and K. H. Ploog

Appl. Phys. Lett. 73, 2176 (1998); http://dx.doi.org/10.1063/1.122414 (3 pages) | Cited 14 times

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We report a time-resolved near-field luminescence study of excitonic real-space transfer into single GaAs quantum wires. Excitons generated by local optical excitation in a 250 nm spot undergo diffusive transport over a length of several microns and are subsequently trapped into the quantum wire by optical phonon emission. Local energy barriers in the vicinity of the quantum wire, originating from the epitaxial growth mechanism of the nanostructure, directly influence the real-space transfer dynamics and trapping efficiency. © 1998 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
63.20.kk Phonon interactions with other quasiparticles
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Nanometer-scale Si selective epitaxial growth on Si surface windows in ultrathin oxide films fabricated using scanning tunneling microscopy

Motoshi Shibata, Yoshiki Nitta, Ken Fujita, and Masakazu Ichikawa

Appl. Phys. Lett. 73, 2179 (1998); http://dx.doi.org/10.1063/1.122415 (3 pages) | Cited 28 times

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Using scanning tunneling microscopy (STM), nanometer-scale Si(111) and Si(001) windows in ultrathin SiO2 films are fabricated by electron-beam-induced thermal decomposition. At 450–630 °C, the oxidized Si surfaces are irradiated with a field emission electron beam from a STM tip with an energy of 70–150 eV and a current of 10–50 nA. The smallest window size is about 40 nm. The shape of the Si crystals selectively grown on the Si(001) windows is that of a frustum of a quadrangular pyramid, while that on the Si(111) windows is an (111) oriented two-dimensional island. We discuss the influence of the field emission electrons on the fabrication and the selective growth. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
61.80.Fe Electron and positron radiation effects
81.65.Mq Oxidation
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Temperature dependence of noise in a GaAs metal-semiconductor field effect transistor at microwave frequencies

J. A. Fendrich and M. Feng

Appl. Phys. Lett. 73, 2182 (1998); http://dx.doi.org/10.1063/1.122416 (3 pages) | Cited 1 time

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Measurements of the noise parameters of a GaAs metal-semiconductor field effect transistor (MESFET) show the minimum noise figure decreases exponentially into the noise floor with decreasing temperature for most frequencies from 2 to 18 GHz and for most currents. The MESFET noise has a thermal activation energy of ∼ 55 meV which is almost half the value seen in a pseudomorphic high electron mobility field effect transistor (pHEMT). Unlike in the pHEMT, the high-temperature coefficient to the activated behavior for the MESFET is independent of current and frequency. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
84.40.-x Radiowave and microwave (including millimeter wave) technology

Electrical and optical properties of CdGeAs2 single crystals irradiated with fast electrons

I. Zwieback, D. Perlov, J. P. Maffetone, and W. Ruderman

Appl. Phys. Lett. 73, 2185 (1998); http://dx.doi.org/10.1063/1.122417 (3 pages) | Cited 14 times

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The effects of 10 MeV fast electron irradiation on conductivity type, resistivity, and optical absorption of CdGeAs2 single crystals were studied. Irradiation of as-grown p-type crystals with a fluence of 1×1017 cm−2 caused compensation of the semiconductor and a marked improvement in the optical transmission. A level of absorption below 0.1 cm−1 at 5 ⩽ λ ⩽ 11 μm was registered. Increase in the fluence to 2×1017 cm−2 led to conversion to n-type, a drop in the resistivity and deterioration of the transmission. Analysis of the absorption in p-type crystals showed that transitions from the V2 and V3 split-off bands to the V1 valence band represent the major absorption mechanism. Splitting energies ΔE2−1 = 0.15 eV and ΔE3−1 = 0.35 eV have been calculated. Absorption in n-type crystals increased as λ2.4 indicating absorption by free electrons and their scattering by optical phonons. The effect of irradiation on the optical absorption of CdGeAs2 is assigned to the radiation-induced changes in the compensation level. © 1998 American Institute of Physics.
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72.80.Jc Other crystalline inorganic semiconductors
61.80.Fe Electron and positron radiation effects
78.40.Fy Semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
63.20.K- Phonon interactions

Preliminary investigation of the kinetics of postoxidation rapid thermal anneal induced hole-trap-precursor formation in microelectronic SiO2 films

J. F. Conley, P. M. Lenahan, and W. F. McArthur

Appl. Phys. Lett. 73, 2188 (1998); http://dx.doi.org/10.1063/1.122418 (3 pages) | Cited 6 times

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Measurements of the growth of E′ center precursor and hole trap precursor densities versus postoxidation anneal time show that both approach saturation values and that the approach to these values is more rapid at higher temperatures. Our results, at least qualitatively, show that a kinetic component can be added to a predictive thermodynamics-based model of oxide hole trapping. The results also indicate quite strongly that a thermodynamics approach to oxide hole trap precursor modeling is appropriate, i.e., the relevant defect densities approach thermodynamic equilibrium or quasiequilibrium in reasonable times. © 1998 American Institute of Physics.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ng Insulators
61.72.Cc Kinetics of defect formation and annealing

Room temperature operation of epitaxially grown Si/Si0.5Ge0.5/Si resonant interband tunneling diodes

Sean L. Rommel, Thomas E. Dillon, M. W. Dashiell, H. Feng, J. Kolodzey, Paul R. Berger, Phillip E. Thompson, Karl D. Hobart, Roger Lake, Alan C. Seabaugh, Gerhard Klimeck, and Daniel K. Blanks

Appl. Phys. Lett. 73, 2191 (1998); http://dx.doi.org/10.1063/1.122419 (3 pages) | Cited 55 times

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Resonant interband tunneling diodes on silicon substrates are demonstrated using a Si/Si0.5Ge0.5/Si heterostructure grown by low temperature molecular beam epitaxy which utilized both a central intrinsic spacer and δ-doped injectors. A low substrate temperature of 370 °C was used during growth to ensure a high level of dopant incorporation. A B δ-doping spike lowered the barrier for holes to populate the quantum well at the valence band discontinuity, and an Sb δ-doping reduces the doping requirement of the n-type bulk Si by producing a deep n+ well. Samples studied from the as-grown wafers showed no evidence of negative differential resistance (NDR). The effect of postgrowth rapid thermal annealing temperature was studied on tunnel diode properties. Samples which underwent heat treatment at 700 and 800 °C for 1 min, in contrast, exhibited NDR behavior. The peak-to-valley current ratio (PVCR) and peak current density of the tunnel diodes were found to depend strongly on δ-doping placement and on the annealing conditions. PVCRs ranging up to 1.54 were measured at a peak current density of 3.2 kA/cm2. © 1998 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
81.05.Cy Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.40.Gk Tunneling

Observation of coherent hybrid reflection with synchrotron radiation

S. L. Morelhão, L. H. Avanci, M. A. Hayashi, L. P. Cardoso, and S. P. Collins

Appl. Phys. Lett. 73, 2194 (1998); http://dx.doi.org/10.1063/1.122420 (3 pages) | Cited 7 times

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High resolution synchrotron radiation has been used to investigate the occurrence of coherent hybrid reflections (CHR) in the In0.49Ga0.51P/GaAs(001) structure. Several ϕ scans at the 002 layer reflection were carried out. The scanned ϕ intervals are correlated by the [001] axis symmetry and should present the same pattern. A break in the symmetry is observed due to constructive/destructive interference of the hybrid amplitudes with the amplitude from the 002 layer reflection. The effects of substrate miscut and interface distance are taken into account to explain the observed patterns. The application of CHR as a high sensitive tool to analyze epitaxial growth is discussed. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
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